Beta-Catenin is a 92 kD protein normally found in the cytoplasm of the cell in the submembranous location. This protein is associated with E-Cadherin and may be essential for the function of E-Cadherin. Mutations in the Beta-Catenin gene result in nuclear accumulation of this protein. Nuclear accumulation of this protein has been demonstrated in fibromatosis lesions of the breast, and abdomen and therefore is useful in differentiating this lesion from other spindle cell lesions that may occur in these locations. Nuclear accumulation of Beta-Catenin has also been demonstrated in colorectal carcinoma.